Problem: Simplify the following expression: $q = \dfrac{4}{5t} - \dfrac{1}{6t}$
Explanation: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5t$ and $6t$ $\lcm(5t, 6t) = 30t$ $ q = \dfrac{6}{6} \cdot \dfrac{4}{5t} - \dfrac{5}{5} \cdot \dfrac{1}{6t} $ $q = \dfrac{24}{30t} - \dfrac{5}{30t}$ $q = \dfrac{24 -5}{30t}$ $q = \dfrac{19}{30t}$